1. Technical Field
The present invention relates to elevation structures, and more particularly, to a screw-driven elevation structure.
2. Description of Related Art
Since population ageing and urban population concentration are ever-increasing, the demand for elevation structures is becoming heavier. A conventional elevation structure usually uses a steel hoist cable and pulleys for driving an elevator car to move up and down so as to convey people or freight from one floor to another in a building. Although the conventional steel hoist cable-style elevation structure not only incurs a low manufacturing cost but also benefits from sophisticated manufacturing technology, it poses an insidious safety issue—a severed steel hoist cable. Elevation structure manufacturers do make persistent efforts to study and improve the safety of the conventional steel hoist cable-style elevation structure. Still, it is not uncommon for elevator cars to plummet because of a severed steel hoist cable. Furthermore, there is still room for improvement in the conventional steel hoist cable-style elevation structure in routine examination and maintenance.
To cope with the aforesaid problems, a screw nut assembly-driven elevation structure is provided. A nut of the screw nut assembly is disposed around a screw thereof and thereby stops the screw from loosening. Hence, the screw nut assembly-driven elevation structure prevents the steel hoist cable from severing which might otherwise end up with a plummeting elevator car. However, not only does the length of the screw has a manufacturing limitation, but stress concentration also occurs to an overly long screw and thus compromises the material strength thereof. Therefore, Taiwan patent 543649 is put forth in an attempt to solve the aforesaid problem. However, Taiwan patent 543649 discloses two power sources which incur a high manufacturing cost, not to mention that the two power sources have to be controlled simultaneously, thereby adding to a control cost. Furthermore, Taiwan patent 543649 discloses a side transmission mechanism which is likely to cause the elevator car to move obliquely and thereby operate unsteadily.